Quick release collet

Abstract

A pipe holding collet is provided with an insert assembly that can be readily and quickly changed without the use of tools so as to adapt the collet to hold tubes of different sizes. The insert assembly is formed of a number of identical longitudinally separate segments, radially urged outwardly by compression springs and held together in a unitary assembly by a segment encircling retainer ring. The radially contractible and expandable assembly is releasably held within the bore of a master collet by means of an interengaging circumferential groove on the inner surfaces of the master collet fingers and circumferential ribs on the outer surfaces of the insert segments.

What is claimed is: 
     
       1. A collet comprising: a master collet having a plurality of resilient collet fingers movable toward radially expanded and contracted positions, said fingers collectively defining an insert receiving bore,   a removable self-contained insert assembly detachably secured in said master collet bore, said assembly being configured and arranged to be manually attachable to and removable from said bore without use of tools, said insert assembly comprising:   a plurality of side by side insert segments having front and back ends,   a plurality of resiliently compressible elements received between adjacent ones of said insert segments for urging said segments radially outwardly,   a retainer ring encircling all of said segments adjacent said front ends thereof for limiting radial outward expansion of the segments and for holding the segments together in a unitary, self-contained assembly when the segments are removed from said insert receiving bore,   said segments being configured to be manually squeezed together to a radially contracted position by radially inwardly directed pressure exerted at said front ends,   a circumferential groove formed in said master collet fingers and opening into said insert receiving bore,   a radially outwardly projecting rib on said inserts collectively, and extending circumferentially around said inserts intermediate said front and back ends, said rib being received in said circumferential grove, said rib having an outer diameter in said contracted position of said segments that is smaller than the diameter of said insert receiving bore when said collet fingers are in said expanded position thereof, said rib having an outer diameter in radially expanded position of said segments sufficient to position the rib in said circumferential groove when said collet fingers are in said expanded position thereof, said rib and groove being configured to enable said segments to be inwardly contracted by manually squeezing said forward ends, thereby withdrawing said rib from said groove and allowing the insert assembly to be substantially simultaneously grasped at said forward ends and pulled from said master collet bore, without use of tools.   
     
     
       2. The collet of claim 1 wherein said rib has an inwardly and forwardly sloping front surface and said groove has an inwardly and forwardly sloping front surface mating with said rib surface, said segments having radially outwardly projecting circumferentially extending lips at said front ends in contact with a front end of said collet fingers, said rib, groove and lip being configured to cause the collet fingers to be a snug fit between the forwardly sloping front surface of the rib and a rear surface of the lip. 
     
     
       3. The collet of claim 1 wherein said segment front ends include an outwardly opening circumferential retainer recess receiving said retainer ring, said retainer recess having an axial extent greater than the axial thickness of said retainer ring to allow each segment front end to be tilted radially inwardly relative to the collet fingers by a distance sufficient to withdraw the rib from the groove and thereby enable release of the segment from the master collet. 
     
     
       4. The collet of claim 1 wherein said compressible elements comprise a plurality of compression springs, said segments having mutually adjacent mating surfaces formed with pairs of mutually opposed and mutually registered spring receiving recesses, each of said springs being individually received in a respective pair of said recesses. 
     
     
       5. The collet of claim 1 wherein said segments each has a circumferentially extending outwardly opening recess receiving said ring, said ring having an axial dimension less than the axial dimension of said recess, to permit each segment to be tilted relative to the ring and to the other segments. 
     
     
       6. The collet of claim 5 wherein said recesses are defined in part by a circumferential front lip on each said segment, said lips collectively having an outer diameter not greater than the inner diameter of said ring, to thereby enable said ring to be moved over said lips into said recesses when said segments are radially contracted. 
     
     
       7. For use with a pipe bending machine of the type having a movable carriage for holding and positioning a pipe to be bent, and wherein pipes of different sizes are inserted into and removed from a pipe holding chuck on the carriage, an improved chuck comprising: an adapter shaft fixed to the carriage at one end thereof and having a forward end,   a master collet having an enlarged rear end portion fixedly secured to the front portion of said adapter shaft, and having an enlarged master collet head, said head and rear portion being interconnected by a relatively thin axially extending master collet body, said master collet head and body being longitudinally separated into a number of master collet fingers, said head having a rearwardly and radially inwardly inclined outer drive surface, and having an inner bore for receiving a collet insert assembly,   a collet housing surrounding said master collet and having a forward end with an inner inclined surface mating with and engaging the inclined outer surface of said collet head,   a hollow drive shaft carried by said carriage for slidable axial motion and having a forward end thereof connected to said collet housing, whereby the collet housing may be axially reciprocated by motion of the drive shaft,   means on the carriage for axially driving the hollow drive shaft,   a removable self-contained insert assembly detachably secured in said master collet bore, said insert assembly comprising: a plurality of side by side insert segments,   a plurality of compression springs respectively received between adjacent ones of said insert segments for urging said segments radially outwardly,   a retainer ring encircling all of said segments for limiting radial outward expansion of the segments and for holding the segments together,     a circumferential groove formed in said master collet head and opening into said bore, and   a radially outwardly projecting rib extending circumferentially around said inserts and received in said master collet head circumferential groove.   
     
     
       8. The apparatus of claim 7 wherein said insert assembly defines a pipe receiving bore having a diameter greater than the diameter of a pipe to be held in said pipe receiving bore, said segments being urged radially outwardly by said compression springs against said master collet inner bore. 
     
     
       9. The apparatus of claim 8 wherein each said segment has an outwardly opening retainer recess section, said sections collectively forming a circumferential retainer recess receiving said retainer ring, said recess having a depth sufficient to allow retention of said retainer ring in the recess during contraction of said insert assembly to a position in which the outer diameter of said rib is not greater than the diameter of said master collet bore, whereby the completely assembled insert may be radially contracted and inserted as a unit into said master collet bore. 
     
     
       10. For use with a pipe bending machine of the type having a movable carriage for holding and positioning a pipe to be bent, and wherein pipes of different sizes are inserted into and removed from a pipe holding chuck on the carriage, an improved chuck comprising: a master collet having a rear end portion secured to said carriage and having an enlarged master collet head, said head and rear portion being interconnected by an axially extending master collet body, said master collet head and at least part of said body being longitudinally separated into a number of master collet fingers, said head having a rearwardly, and radially inwardly inclined outer drive surface, and having an inner bore or receiving a collet insert assembly,   a collet housing surrounding said master collet and having a forward end with an inner inclined surface mating with and engaging the inclined outer surface of said collet head,   a drive shaft carried by said carriage for slidable axial motion and having a portion thereof connected to said collet housing, whereby the collet housing may be axially reciprocated by motion of the drive shaft,   means on the carriage for axially driving the drive shaft, and   a removable self-contained insert assembly detachably secured in said master collet bore, said insert assembly comprising: a plurality of side by side insert segments,   a plurality of resilient compressible elements respectively received between adjacent ones of said insert segments for urging said segments radially outwardly,   a retainer ring encircling all of said segments for limiting radial outward expansion of the segments and for holding the segments together,     a circumferential groove formed in said master collet head and opening into said bore, and   a radially outwardly projecting rib extending circumferentially around said inserts and received in said master collet head circumferential groove.   
     
     
       11. The apparatus of claim 10 wherein said insert segments have front and back ends, wherein said rib is located substantially forward of said back end, and wherein said segments are configured to be manually squeezed together at the front ends thereof into a retracted position in which said rib is manually withdrawn from said groove to allow the insert assembly to be grasped to a front end thereof and pulled from said master collet. 
     
     
       12. The apparatus of claim 11 wherein said rib has an inwardly and forwardly sloping front surface and said groove has an inwardly and forwardly sloping front surface mating with said rib surface, said segments having radially outwardly projecting circumferentially extending lips at said front ends, said lips having a rear surface in contact with a front end of said collet fingers, said rib, groove and lip being configured to cause the collet fingers to be a snug fit between the forwardly sloping front surface of the rib and said rear surface of the lip. 
     
     
       13. The apparatus of claim 11 wherein said segment front ends include an outwardly opening circumferential retainer recess that receives said retainer ring, said retainer recess having an axial extent greater than the axial thickness of said retainer ring to allow each segment front end to be tilted radially inwardly relative to the collet fingers by a distance sufficient to withdraw the rib from the groove and thereby enable release of the segment from the master collet.